• cold solder, crack board or even possibly a break in the flex cable (likely);

• touch screen / digitizer (most likely).

All of the above would require that the unit be opened up for visual inspection, voltage/continuity/resistance checks, confirm faults and effect repairs.

Are you then considering a DIY (do-it-yourself) repair approach? If yes, do you have access to and familiar with a multi-meter and even perhaps a soldering iron? Equally important, could you make use of the schematic diagrams?